1. Field of the Invention
The present invention generally relates to wave frequency calibration method and device for remote controller, more particularly, to wave frequency calibration method and device for remote controller that employs resistor-capacitor type oscillator.
2. Description of the Prior Art
Remote controller is wildly used in our daily life and is applied in many filed, e.g. security equipment, house appliances, audio/video equipment and air conditioner, etc., in which remote controller had played an important roll for improving the convenience of usage.
Please refer to FIG. 1, which is a diagram showing an operation flow of a remote controller in accordance to prior arts. As seen, the remote controller comprises a transmitting end 1 and a receiving end 2. The transmitting end 1 further comprises: an oscillator 11 for generating a carrier wave 110 based on a designated frequency; a controller 12 for generating a control instruction 120 based on an user's instruction; a modulator 13 connected to the oscillator 11 and the controller 12, for generating an output signal 130 by modulating the carrier wave 110 and the control instruction 120; a transmitter 14 for outputting the output signal 130 by a wireless method, such as using infrared or radio frequency. In order to avoid interference, the receiving end 2 usually is designed to receive the carrier wave 110 of a predetermined frequency. After receiving the output signal 130, the receiving end 2 will demodulate and recover the control instruction 120, and complete the whole work based on the instruction.
To assure the output signal 130 be received by the receiving end 2, an accurate carrier wave 110 is required, hence, an advanced and sophisticated oscillator is required for faithfully generating the stationary carrier wave 110. The crystal oscillator is commonly used in the industry for having characteristics of high stability and high accuracy. However, the sophisticated crystal oscillator is very expensive that it takes almost one fourth of total cost of the remote controller. Therefore, seeking the best replacement of the expensive crystal oscillator, i.e. an oscillator 11 with low cost, is the major and common concern in the industry.
Another commonly used oscillator in the market is the so-called resistor-capacitor type oscillator (RC oscillator), which is an oscillator constructed using the resonance characteristic happened between a resistor and a capacitor. Although the cost of the RC oscillator is relatively low, however, its quality is not stable since the property of the resistor and capacitor is subject to change due to the variation of temperature of the environment. General speaking, the error of the resistor is around 5˜20%, and the error of the capacitor is around 20˜30%. The oscillating frequency of a RC oscillator is related to the product of the resistance and the capacitance, therefore, the error of the RC oscillator can be as high as more than 50%, which is a major concern when the RC oscillator is put into use as an oscillator inside the remote controller, even though it has the advantage of low cost.
Therefore, the present invention can provide a method and a device of wave frequency calibration for remote controller. Incorporating the present invention with a RC oscillator, the foregoing problem of the bias of wave frequency can be avoid, which enables the RC oscillator to be an oscillator which can be used commonly and widely in remote controller for lowing production cost.